Wednesday, 8 September 2010

How To Determine And Use A Grid Reference On A Mountain Map

When you are using a mountain map there are a number of advantages to using grid references. They are great for pin pointing your location on a mountain map.

Think about it. You are stuck on a mountain and you look at your mountain map and find a grid reference for where you are and call the emergency services and they can rescue you directly because you have pin pointed you reference. So a very useful thing to learn and not really difficult.

There are mainly two types of grid reference, a four figure which gives you a square for your location and a six figure grid reference which gives you any exact location on your mountain map.

If you look at an ordinance survey mountain map you will see a full grid of squares on the actual mountain map. The actual grid squares are made of grid lines (normally light blue) that are labelled both as a vertical and horizontal. The vertical lines run from the top to the bottom of the map with each line being marked with a number 01, 02, 03 etc. This is as you would expect.

Similarly the horizontal lines run from the left hand side to the right hand side of the mountain map and are labelled on both sides in the same way 01, 02, 03 etc.
When you use a 4 figure grid reference on a mountain map you will simply reference a square in the grid as mentioned above. This is determined by the horizontal reference (lets say 06) first and then the vertical reference (lets say 10). It is always in this order. How is a good way to remember this?

A good way to remember this I have found is the words "along the corridor (horizontal) and up the stairs (vertical)" - on our mountain map. So in this example for these numbers the 4 figure grid reference (which is a grid square on the map) is 0610.

However to pinpoint this location on a mountain map a more accurate 6 figure grid reference is used. We actually still use the 4 figure grid reference with another 2 figures or numbers. This will pin point the location within the square of the 4 figure reference.

Firstly take the Horizontal grid line 06 and look at the next horizontal line 07. You should imagine the space between 06 and 07 as split into 10 more grid lines and set an estimated figure from 1-10. So horizontally if you believe the location is a quarter way between 06 and 07 then the horizontal ref is 062. If you believe the location is a third from 06 to 07 you could say the horizontal ref is 063 etc. Let us say that it is 063 on our mountain map.

Next you do exactly the same on the vertical grid lines. The vertical ref is going to be between 10 and 11 in our example. You should imagine 10 small grid lines between 10 and 11 and allocate a number where your location is vertically 1-10. Let us say you think it is about 4. So our vertical grid ref is 104. Now put the 2 grid refs together - again "along the corridor (horizontal) and up the stairs (vertical)". So our 6 figure ref on our mountain map is 063104

By using a 6 figure reference we can accurately pin point where a location is on the mountain map.

Again the benefits are vast. For less dramatic example you can use this to start and finishes of hikes. Scout hike patrols are given a 6 figure reference to start and finish. They then make their own route between these 2 references. It is a great exercise.

Have a great mountain hike with your mountain map.

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